Sprint has reduced the price of the iPhone 4S on its mobile network in the US, you can now pick up a 16GB iPhone 4S on Sprint for $149.99 when you sign up to a new two year contract with the carrier.
If you want the 32GB version this will set you back $249.99 with a new two year contract, and the 64GB version is $349.99 with a new two year contract with Sprint.
The price drop appears to be a permanent one, and Sprint are obviously looking to sell as many of their iPhone 4S inventory before the new iPhone 5 is released next month.
Source Brief Mobile
Have a look at the difference between the iPhone 4 and iPhone 4S.